Lower-Extremity Injuries Predominate in American High School Tennis Players

Purpose To describe injury epidemiology in U.S. adolescent tennis players between 2014 and 2018 via the High School Reporting Information Online (HS RIO) database. Methods The HS RIO database was queried for injury data on high school tennis players as reported by athletic trainers between 2014 and 2018. Injuries were analyzed according to athlete demographics, injury type, location, and context. Variables of interest between male and female athletes were compared using Pearson χ2 test or Fisher exact test. Results In total, 176 injuries in high school tennis players between 2014 and 2018 were identified in the HS RIO database. Overall, 25.6% (45/176) occurred in the ankle, 12.5% (22/176) in the knee, and 9.7% (17/176) in the wrist. The most common types of injuries were ligament sprains and muscle strains at 35.2% (62/176) and 17.6% (31/176) of injuries, respectively. Although most injuries were unrelated to contact, such as overuse and heat exertion or stroke, 28.7% (47/176) of injuries were the result of rotation around a planted foot/inversion of the foot. We found no difference in injury patterns between male and female high school tennis athletes. Conclusions We found no difference in injury patterns between male and female U.S. high school tennis athletes. The ankles, knees, and wrists were the most commonly injured areas in this population. The most common types of injuries were ligament sprains and muscle strains. Although many injuries were new, athletes rarely required surgery and returned to play. Finally, we found no difference in injury patterns between male and female high school tennis athletes. Clinical Relevance The epidemiology of injuries among high school tennis players is poorly understood. The information from this study will help us to understand these injuries and how we may be able to better prevent them.

T he International Tennis Federation estimates that more than 87 million people across the world play tennis as of 2021, an increase of 4.5% compared with 2018. 1 Participation levels vary globally, from recreational to professional and across different categories including men's, women's, doubles, and wheelchair tennis.A snapshot of tennis participation shows 7,275 ranked players in International Tennis Federation Junior World Tennis Tour and 3,619 professional players with an Association of Tennis Professionals or Women's Tennis Association ranking. 1 Tennis requires a balance of agility, flexibility, and power that is distinct from other racquet sports. 2 Proper technique delivered through a kinetic chain traveling from the ground through the lower limbs, trunk, upper extremity, and into the racquet drives the tennis ball across the court. 3,4In addition, tennis players must navigate the court effectively, running, stopping, and changing direction at a moment's notice.Therefore, the forces needed to perform these strokes and movements place considerable strain on the tennis players' musculoskeletal system, oftentimes leading to injury. 5,6revious studies have described the epidemiology of injuries in tennis players.In a meta-analysis, Pluim et al. 7 concluded that injuries in tennis players were most common in the lower extremities, followed by the upper extremities, and then finally the trunk.In a review, Dines et al. 8 stated that most lower-extremity injuries were acute and included sprains or strains, whereas most upper-extremity injuries were chronic, particularly elbow tendinopathies.Although injury rates across levels of competition, sex, and age have been compared, the reports have been inconsistent. 2,7,9o date, most studies in the literature on tennis injury epidemiology have focused on a single cohort of competitors or particular demographic. 10,11For instance, a previous survey of injuries using the National Collegiate Athletic Association Injury Surveillance Program only focused on U.S. men's and women's college tennis and found similar injury rates overall between men and women. 12Another survey by Hutchinson et al. 9 focused solely on injuries within United States Tennis Association's boys' tennis.However, a review of the literature reveals a gap in injury epidemiology for high school tennis players within the United States.
Given that these individuals are still physically growing and mentally maturing, high school athletes can be particularly vulnerable to injury. 135][16] Although these studies have focused more on major sports such as basketball, soccer, football, baseball, and softball, injury epidemiology for U.S. adolescent tennis athletes also should be analyzed to help inform coaches, trainers, parents, and players on injury-prevention strategies. 17This study uses data from the High School Reporting Information Online (HS RIO) database to report injuries suffered by U.S. high school tennis athletes.
The purpose of this study is to describe injury epidemiology in U.S. adolescent tennis players between 2014 and 2018 via the HS RIO database.We hypothesized that high school tennis athletes would experience mostly lower-extremity injuries, similar to other populations of tennis players.

Data Collection
The HS RIO database was queried to collect data on injuries in U.S. high school tennis players from 2014 to 2018 from more than 100 participating high school across the United States.The HS RIO has been validated and methods of data collection have been described. 18he HS RIO database monitors injuries and athletic exposures described as school-sanctioned practices and competitions as reported by each institution's athletic trainer(s) (AT).Each report contains information on the injured athlete, including athlete demographics, injury, and injury context.Athlete demographics contain information about the athlete's age, height, weight, sex, and school year.Injury information refers to the diagnosis, severity, and anatomical location.
Injury context refers to the situation in which the injury occurred, such as during practice or competition, preseason, or postseason and other sport idiosyncrasies.This study was reviewed and granted an institutional review board exemption.

Data Analysis
The categorical variables are summarized as frequency (percentage).The variables of interest were compared between male athletes and female athletes using Pearson c 2 test or Fisher exact test when appropriate.All statistical analyses were conducted using RStudio software (RStudio 4.0.3;PBC, Boston, MA) and 0.05 was chosen as the cut-off criterion for statistical significance.

Injury by Year and Level of Play
A total of 176 injuries in high school tennis players were identified in the HS RIO   1).

Principal Body Part Injured, Injury Type, and Mechanism of Injury
Overall, 25.6% (45/176) occurred in the ankle, 12.5% (22/176) in the knee, and 9.7% (17/176) in the wrist.Injuries to the eyes, nose, and upper arm were recorded, but rare at 0.6% (1/176) of injuries (Table 1).The most common types of injuries were ligament sprains and muscle strains at 35.2% (62/176) and 17.6% (31/176) of injuries, respectively.Acute cardiac events, abrasions, stress fractures and avulsions were noted, but rare at 0.6% (1/176) of injuries (Table 2).Regarding the general mechanism of injury, 44% (77/176) of injuries occurred acutely and without contact, whereas 24.0% (42/176) were considered chronic.Analysis of tennisspecific mechanisms of injury reiterated that although most injuries were unrelated to contact such as overuse and heat exertion or stroke, 28.7% (47/176) of injuries were the result of rotation around a planted foot/ inversion of the foot (Table 3).

Discussion
The most important finding of this study is that the ankle, knee, and wrist are the most common locations for injuries seen in high school tennis players.The most common types of injuries were ligament sprains and muscle strains in the lower extremity.Injuries were also most attributed to overuse.Although few studies in the literature mention the context of injury, we note that most noncontact injuries occurred during general play or while chasing a ball.Fortunately, nearly one half of all athletes returned to play within a week of injury, and few required surgery.
In our study population consisting of American high school tennis players, we found the ankles and the knees to be the 2 most common body parts injured.This has been previously shown in other demographics, as well.For instance, one study involving 55 Swedish junior tennis players found lower-extremity injuries, representing 51% of all injuries, to be the most common location of tennis injuries. 10In contrast, other studies involving elite junior Australian tennis players and boys participating in the United States Tennis  Association's National Boys' Tennis Championships both reported back injuries to be the most common. 9,11his difference in findings may be attributed to level of play.Because most participants in this study did not play tennis outside of school, they may have been less prone to overuse injuries involving the trunk compared to elite-level adolescent players, who may be playing at a greater intensity and/or frequency.
Our findings for injury type and injury mechanism were similar to those found in other studies of tennis athletes.For example, we found strains and sprains to be the most common injury types, with fractures and dislocations being rare.These results are similar to those of Dines et al. 9 in youth and pediatric tennis players in the United States.In addition, we determined overuse to be the most common mechanism of injury.This result is echoed by findings from Johansson et al. 10 of a significant increase in injury risk in relation to the volume of work and training their tennis athletes underwent.The relationship between overuse and injury has been further reiterated by Myers et al., 19 who found that athletes who underwent an acute increase in training load were at greater risk of getting injured.
Our study did not find any appreciable differences in injuries among male and female tennis players.The differences between male and female injuries may be attributed to the level of competition found in our population.We expect that the intensity of play and level of skill in school-sanctioned events and competitions may differ from those found in amateur and professional tennis.However, a review of the literature on sex-based differences in injuries among young tennis players have returned with disparate results.Several studies on elite, youth tennis players outside the United States found no significant injuries between male and female players. 11,20In contrast, a report on elite, junior players in Sweden found that male players suffered mainly from ankle injuries, whereas female players most commonly had knee injuries. 21Another study done in Spanish tennis academies also found that male players suffered more from lower-limb injuries, as compared to female players, who more commonly suffered trunk injuries. 22njury outcomes are a critical topic in sports injury epidemiology studies, especially for adolescent athletes.Previous work on Australian junior tennis players reported greater injury severity for male players compared with female players, defined as a greater amount of time away from play. 11They reported 3.6 AE 0.6 days lost in male players compared with 1.1 AE 0.9 days lost in female players.Our study found that more than 50% of the injured tennis players in this study were able to return to play within 6 days from the injury, and only 2.2% of players required surgical treatment.

Limitations
This study is not without limitations.It should be noted that population size was limited in our study because the HS RIO only contains data on tennis injuries reported from the 2014/2015-2017/2018 academic years at more than 100 participating high schools.Because of this limited time frame, the generalizability of our results may be affected.Owing to the limited sample size, limitations to the generalizability of this study are due to convenience sampling.Because of this, we were unable to calculate injury rates or ratios and make further inferences.In addition, since the HS RIO database relies on injury reporting from ATs at each high school across the nation, there may be reporting bias.For instance, under-reporting of injuries due to variability in judgment or record-keeping by each AT should be considered.

Conclusions
We found no difference in injury patterns between male and female U.S. high school tennis athletes.The ankles, knees, and wrists were the most commonly injured areas in this population.The most common types of injuries were ligament sprains and muscle strains.Although many injuries were new, athletes rarely required surgery and returned to play.Finally, we found no difference in injury patterns between male and female high school tennis athletes.

Table 2 .
Injury Type *Fisher exact test for count data.

Table 4 .
Return to Play *Fisher exact test for count data.

Table 3 .
Injury Mechanisms *Fisher exact test for count data.

Table 1 .
Injury by Year, Level of Play, Injury by Time of Tennis Season, Injury Incidence, Injury Context, and Surgery Requirement